Molecular analysis of lichen-associated bacterial communities

Abstract

The bacterial communities associated with 11 different lichen samples (belonging to eight different species) from different habitats were investigated. The culturable aerobic-heterotrophic fraction of the bacterial communities was isolated from nine lichen samples on protein-rich and sugar-rich/N-free media. Thirty-four bacterial isolates were purified and pooled into groups (phylotypes) by analysis of the ribosomal internal transcribed spacer polymorphism. Twenty five phylotypes were identified, each comprising between one and three isolates. One isolate of each phylotype was partially sequenced and the resulting 16S rRNA gene sequences were compared in a phylogenetic analysis. Three genera of Firmicutes, four of Actinobacteria and three of Proteobacteria were identified. Two phylotypes, belonging to the phyla Actinobacteria and Proteobacteria, respectively, were not identified at genus level. Some bacterial taxa were retrieved frequently in different lichen species sampled in the same or different sites. Paenibacillus and Burkholderia phylotypes seem to be common in lichens. Luteibactor rhizovicina was found in three different lichens of two different regions. In a cultivation-independent approach, total DNA was extracted from 11 lichen samples. Molecular fingerprints of the bacterial communities were obtained by PCR-amplification of the internal transcribed spacer region, and sequencing of selected bands indicated the presence of additional bacteria.